When a framework member for a vehicle receives a load due to a collision or the like, it is elastically budded by a compressive stress locally on the compression side of a bend, since it is weaker on the compression side than on the tension side. Therefore, some framework members for vehicles are formed to have a closed cross sectional structure in which a reinforcement member is disposed only on the compression side of a bend (see Japanese Patent Application Publication No. 2003-731483 (JP-A-2003-231483)). FIG. 5 shows a B-pillar 100 as an example of such framework members. The B-pillar 100 is made up of a pillar outer panel 101 and a pillar inner panel 102 defining a closed cross section, an outer reinforcement 103 and a hinge reinforcement 104 disposed on the compression side of a bend as reinforcing members, and a reinforcement 105 disposed at the middle as a reinforcing member.
In the framework member for a vehicle shown in FIG. 5, the neutral axis of a bend between the compression side and the tension side is positioned in the vicinity of the center of the closed cross section (see the neutral axis A of FIG. 5). Therefore, a compressive stress field extends over a large region in a vertical wall part coupling the compression-side surface and the tension-side surface, and thus a compressive stress acts on the vertical wall part besides the compression-side surface. As a result, the compression side of the framework member is subjected to elastic buckling due to the compressive stress, which progresses locally. In the B-pillar 100 shown in FIG. 5, a local dent H is formed in an outer surface 101a of the pillar outer panel 101 at the moment when such buckling starts.
In order to prevent such elastic buckling due to a compressive stress, it is necessary to improve the stiffness (rigidity) of the compression side. For that purpose, conventional framework members for vehicles are provided with a number of reinforcing members for the compression-side surface and the vertical wall part. As a result, the mass and the cost are unfavorably increased.